Instruments of this type, called morcellators, are used in endoscopic interventions required for the removal of large portions of tissue. These morcellators consists of a powered cutting tube, which can be introduced directly into the body or into a natural or artificially produced body cavity. To remove tissue, a gripping pincer is introduced through the cutting tube into the body or body cavity to grasp the tissue that is to be removed. If the pincer is then withdrawn and if the tissue is pressed against the cutting edge of the rotating morcellator, a cylindrically shaped block of tissue can be cut out and removed through the tube by carefully measured pulling and possibly varying the rotation speed and rotation direction. Even large amounts of tissue can be extracted in this way within a few minutes.
Generic medical instruments are described for instance in EP-B1-0 555 803 and EP-A1-0 806 183. In these morcellators known from the art, the rotating drive of the cutting tube is carried out by a tooth-wheel and/or worm gear held in place between the motor and the cutting tube.
The use of these gears which serve to transmit the rotation force, however, can cause considerable capacity losses in the actual motor power. In addition the drives are sometimes very complex in structure and thus also quite expensive.